Small cell lung cancer
Small cell lung cancer (SCLC), also known as oat cell lung cancer, is a subtype of bronchogenic carcinoma separated from non-small-cell lung cancer (NSCLC) as it has a unique presentation, imaging appearances, treatment, and prognosis. SCLCs are neuroendocrine tumors of the lung that rapidly grow, are highly malignant, widely metastasize, and, despite showing an initial response to chemotherapy and radiotherapy, have a poor prognosis and are usually unresectable.
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Epidemiology
Small cell lung cancers represent 15-20% of lung cancers 1 and are strongly associated with cigarette smoking.
Clinical presentation
Clinical presentation can significantly vary and can present in the following ways:
- constitutional
- fever
- weight loss
- malaise
- primary tumor
- cough
- hemoptysis
- dyspnea
- local invasion
- dysphagia (esophageal compression)
- hoarseness (recurrent laryngeal nerve palsy)
- stridor (airway compression)
- SVC obstruction
- rib erosion
- metastatic spread (affecting ~70% of patients are presentation)
- bone pain (bone metastases)
- focal neurological deficit (CNS involvement)
- right upper quadrant pain (liver metastases)
- paraneoplastic syndromes
Pathology
Small cell carcinoma is considered a neuroendocrine tumor of the lung. It arises from the bronchial mucosa. Local invasion occurs in the submucosa with subsequent invasion of peribronchial connective tissue. Cells are small, oval, with scant cytoplasm and a high mitotic count.
It is the most common lung cancer subtype to produce necrosis, superior vena cava (SVC) infiltration/SVC obstruction, and paraneoplastic syndromes (see bronchogenic carcinoma).
Location
Approximately 90-95% of SCLCs occur centrally, usually arising adjacent to a lobar or main bronchus 3.
Radiographic features
As previously mentioned, small cell tumors are located centrally in the vast majority of cases. They arise from the mainstem of the lobar bronchi and thus appear as hilar or perihilar masses 2, and frequently have mediastinal lymph node involvement at presentation.
Plain radiograph
Appearances on chest x-rays are non-specific. They may be seen as a hilar/perihilar mass usually with mediastinal widening due to lymph node enlargement 2. In fact, the mediastinal involvement is often the most striking feature and the primary mass may be inapparent.
CT
On CT, mediastinal involvement may appear similar to lymphoma, with numerous enlarged nodes. Direct infiltration of adjacent structures is more common. Small cell carcinoma of the lung is the most common cause of SVC obstruction, due to both compression/thrombosis and/or direct infiltration 2.
SCLCs are usually characterized as a mass lesion, where necrosis and hemorrhage are both common. Only rarely do they present as a solitary pulmonary nodule.
For tumor staging, please refer to the article on IASLC (International Association for the Study of Lung Cancer) 8th edition lung cancer staging system (since 2013, small cell lung cancer is staged in the same way as non-small cell lung cancer).
Treatment and prognosis
Most cases will present in advanced stages, be inoperable, and with a dismal prognosis. Only about 5% of patients present at an early stage (Ia, Ib, or IIa), with a potentially curable disease. These patients are usually managed with aggressive chemoradiation therapy and, a few, with lobectomy associated with mediastinal lymph node dissection 4,5.
Surgical excision is commonly not recommended beyond these early stages, as studies have shown that any nodal involvement (N1–3 disease) will not benefit from the excisional treatment 4,5.
Brain metastases are found in up to a quarter of patients at presentation 4 and are known as a common site of disease recurrence after an initial treatment response. Prophylactic cerebral irradiation (PCI) can be offered for those with adequate systemic control and without metastases to the CNS 4.
Advanced disease (stage IV) is managed only with chemotherapy, primarily for palliation and symptom control.
Differential diagnosis
Imaging differential considerations include:
Related Radiopaedia articles
Chest
- imaging techniques
-
chest x-ray
-
approach
- adult
- pediatric
- neonatal
-
airspace opacification
- differential diagnoses of airspace opacification
- lobar consolidation
-
atelectasis
- mechanism-based
- morphology-based
- lobar lung collapse
- chest x-ray in the exam setting
- cardiomediastinal contour
- chest radiograph zones
- tracheal air column
- fissures
- normal chest x-ray appearance of the diaphragm
- nipple shadow
-
lines and stripes
- anterior junction line
- posterior junction line
- right paratracheal stripe
- left paratracheal stripe
- posterior tracheal stripe/tracheo-esophageal stripe
- posterior wall of bronchus intermedius
- right paraspinal line
- left paraspinal line
- aortic-pulmonary stripe
- aortopulmonary window
- azygo-esophageal recess
- spaces
- signs
- air bronchogram
- big rib sign
- Chang sign
- Chen sign
- coin lesion
- continuous diaphragm sign
- dense hilum sign
- double contour sign
- egg-on-a-string sign
- extrapleural sign
- finger in glove sign
- flat waist sign
- Fleischner sign
- ginkgo leaf sign
- Golden S sign
- Hampton hump
- haystack sign
- hilum convergence sign
- hilum overlay sign
- Hoffman-Rigler sign
- holly leaf sign
- incomplete border sign
- juxtaphrenic peak sign
- Kirklin sign
- medial stripe sign
- melting ice cube sign
- more black sign
- Naclerio V sign
- Palla sign
- pericardial fat tag sign
- Shmoo sign
- silhouette sign
- snowman sign
- spinnaker sign
- steeple sign
- straight left heart border sign
- third mogul sign
- tram-track sign
- walking man sign
- water bottle sign
- wave sign
- Westermark sign
-
approach
- HRCT
-
chest x-ray
- airways
- bronchitis
- small airways disease
-
bronchiectasis
- broncho-arterial ratio
- related conditions
- differentials by distribution
- narrowing
-
tracheal stenosis
- diffuse tracheal narrowing (differential)
-
bronchial stenosis
- diffuse airway narrowing (differential)
-
tracheal stenosis
- diverticula
- pulmonary edema
-
interstitial lung disease (ILD)
- drug-induced interstitial lung disease
-
hypersensitivity pneumonitis
- acute hypersensitivity pneumonitis
- subacute hypersensitivity pneumonitis
- chronic hypersensitivity pneumonitis
- etiology
- bird fancier's lung: pigeon fancier's lung
- farmer's lung
- cheese workers' lung
- bagassosis
- mushroom worker’s lung
- malt worker’s lung
- maple bark disease
- hot tub lung
- wine maker’s lung
- woodsman’s disease
- thatched roof lung
- tobacco grower’s lung
- potato riddler’s lung
- summer-type pneumonitis
- dry rot lung
- machine operator’s lung
- humidifier lung
- shower curtain disease
- furrier’s lung
- miller’s lung
- lycoperdonosis
- saxophone lung
-
idiopathic interstitial pneumonia (mnemonic)
- acute interstitial pneumonia (AIP)
- cryptogenic organizing pneumonia (COP)
- desquamative interstitial pneumonia (DIP)
- non-specific interstitial pneumonia (NSIP)
- idiopathic pleuroparenchymal fibroelastosis
- lymphoid interstitial pneumonia (LIP)
- respiratory bronchiolitis–associated interstitial lung disease (RB-ILD)
- usual interstitial pneumonia / idiopathic pulmonary fibrosis (UIP/IPF)
-
pneumoconioses
- fibrotic
- non-fibrotic
-
lung cancer
-
non-small-cell lung cancer
-
adenocarcinoma
- pre-invasive tumors
- minimally invasive tumors
- invasive tumors
- variants of invasive carcinoma
- described imaging features
- adenosquamous carcinoma
- large cell carcinoma
- primary sarcomatoid carcinoma of the lung
- squamous cell carcinoma
- salivary gland-type tumors
-
adenocarcinoma
- pulmonary neuroendocrine tumors
- preinvasive lesions
-
lung cancer invasion patterns
- tumor spread through air spaces (STAS)
- presence of non-lepidic patterns such as acinar, papillary, solid, or micropapillary
- myofibroblastic stroma associated with invasive tumor cells
- pleural invasion
- vascular invasion
- tumors by location
- benign neoplasms
- pulmonary metastases
- lung cancer screening
- lung cancer staging
-
non-small-cell lung cancer